GMAT Question of the Day – Problem Solving – Puzzle

If each term of the sequence K1 + K2 + … + Kn is either 9 or 99 and the sum of the sequence is 495 which of the following could be a value of n^2?

A. 2025

B. 2050

C. 3105

D. 3200

E. 3380

[spoiler]A.[/spoiler]

GMAT Question of the Day Solution

This is a great time to make a chart so that you can see what your options are. Take your time and be organized with this. It may take you an extra few seconds to get started but being methodical will pay off. Start at the extreme using only 9’s and build your way up. You should start to notice a pattern developing. All of the values for n end in 9. We’ll be looking for n squared so the answer must end in 5. Eliminate B, D, and E. We have two choices but one is greater than the maximum 55*55. You can do the multiplication using distribution.

Additional GMAT Puzzle Practice Questions

This is a nearly identical question from the GMAT prep tests 1 and 2: If each term in the sum a₁ + a₂ + a₃ +…+ a_n is either 7 or 77 and the sum equals 350, which of the following could be equal to n?

Here’s a GMAT Puzzle from the GMAT Prep tests that requires similar organization skills: The number 75 can be written as the sum of the squares of 3 different positive integers

And one more algebra, number properties, puzzle question that benefits from a basic setup: If x and y are positive integers such that y is a multiple of 5 and 3x + 4y = 200, then x must be a multiple of which of the following?